1. Field of the Invention
The present invention relates to a retrieval basket device which is introduced into the body through a treatment tool insertion channel of an endoscope.
2. Description of the Related Art
A typical retrieval basket device for an endoscope is provided with a control wire and a basket which is connected to the distal end of the control wire. The control wire is inserted into a flexible sheath to be freely movable in the flexible sheath along an axial thereof. The flexible sheath is introduced into the body through a treatment tool insertion channel of an endoscope. The basket is made of a plurality of resilient metal wires. These metal wires bulge due to the resiliency thereof when the control wire is moved in a direction to make the metal wires project out (bulge) of the distal end of the flexible sheath, and the metal wires become narrow when the control wire is moved in the other direction to sheathe the metal wires in the distal end of the flexible sheath.
By using such a retrieval basket device, a gallstone lodged in a bile duct can be caught from the side of the duodenum and extracted from the bile duct.
FIG. 6 shows a state where a basket 105 which projects out of the distal end of a flexible sheath 2 introduced into the duodenum 100 through a treatment tool insertion channel 51 provided in an insertion tube 50 of an endoscope. If a large gallstone 200 exits in a bile duct 101 as shown in FIG. 6, it is often the case that the gallstone 200 does not easily slip into the basket 105.
If the gallstone 200 captured in the basket 105 is too large to pass through an exit (Vater""s papilla) 102 of the bile duct 101 which is constricted by a constrictor, there is a possibility that the gallstone 200 cannot be removed from the basket 105 and that the basket 105 be stuck in the bile duct 101.
An object of the present invention is to provide a retrieval basket device used for an endoscope which can easily catch large foreign matter and which can release the same easily as necessary.
To achieve the object mentioned above, according to an aspect of the present invention, a retrieval basket device is provided, including a flexible sheath, a control wire which is inserted in the flexible sheath to be movable therein along an axis of the flexible sheath, and a basket constructed from a plurality of resilient wires and connected to a distal end of the control wire, wherein advancing and retreating movements of the control wire in the flexible sheath cause the basket to project out of, and retract into, a distal end of the flexible sheath whereby the basket bulges and narrows, respectively. The plurality of resilient wires are positioned at non-uniform angular intervals as viewed from the axial direction of the control wire.
Preferably, the plurality of resilient wires are positioned so that a first angular interval between two adjacent resilient wires of the plurality of resilient wires is greater than a second angular interval between any other two adjacent resilient wires of the plurality of resilient wires.
In an embodiment, the first angular interval is equal to or greater than an angular interval which is double that of the second angular interval.
In an embodiment, an angular interval between the two adjacent resilient wires positioned at the first interval about an axis of the basket is in a range of approximately 60 through 90 degrees.
In an embodiment, each of the two adjacent resilient wires positioned at the first angular interval is more flexible than any other resilient wires of the plurality of resilient wires.
Preferably, the plurality of resilient wires bend at more than two points on each of the plurality of resilient wires to form the shape of the basket.
In an embodiment, all resilient wires of the plurality of resilient wires except the two adjacent resilient wires, positioned at the first interval, are arranged at approximately equal angular intervals.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-310262 (filed on Oct. 11, 2000) which is expressly incorporated herein by reference in its entirety.